Plant for continuous production of cellulose triacetate in a heterogeneous phase

ABSTRACT

A plant for continuous production of cellulose triacetate in a heterogeneous phase, comprising consecutively arranged apparatus for activating, acetylation and benzene washings, benzene stripping, partial saponification, water washings and final product drying. The apparatus for activating, the apparatus for acetylation and benzene washings, the apparatus for benzene stripping and the partial saponification apparatus are interconnected by connecting adaptors for conveying the fibrous reaction mass from one apparatus to another and provided with means for creating therein a sealing plug from the conveyed reaction mass. Said means for the creation of the sealing plug is in the form of a screw conveyer with a valve arranged at its discharge orifice and spring-loaded in the direction opposite to the direction of the fibrous reaction mass conveying.

United States atet 91 Mikhalsky et al.

[ PLANT FOR CONTINUOUS PRODUCTION OF CELLULOSE TRKACETATE IN A HETEROGENEOUS PHASE [76] Inventors: Fedor Mikhaillovich Milrhalslky,

Zanevsky prospekt, l3, kv. 8; Artemy Mikhailovicln Gaspariants, ulitsa Tukhachevskogo, 37, kv. 84; Jury Nikolaevich Purlov, prospekt Morisa Toreza, 108, kv. 37, all of Leningrad; Pavel llvanovich Kulesh, ulitsa Schedrina, 2, kv. l2, Shostka Sumskoi oblasti; Pavel Petroviclh Rudenko, ulitsa Krasnaya, 200, kv. 24; Alexei Nikolaevich Ryabtsev, ulitsa Zakharova, l6, kv. 7, both of Krasnodar, all of USSR; Yalrov Etimovich Levi, deceased, late of Moscow, USSR; Mina Neukhovna Levi, administratrix, Belyaevo-Bogorodskoe, kvartal 45, korpus 22, kv. 26, Moscow, USSR.

22 Filed: July 19,1971

21 Appl. No.: 163,700

[52] US. Cl 23/260, 23/290.5, 260/229,

. 260/230,l 6 2i177 [5 1] Int. Cl. B0lj 3/02, BOlj 4/00, C081 7/02 [58] Field of Search 23/260, 270, 290.5;

[4 1 Jan. 15, 1974 Zies et al. 23/270 R Clevy et a1 260/229 Primary Examiner.larnes H. Tayman, Jr. Att0rneyHolman & Stern 57 ABSTRACT A plant for continuous production of cellulose triacetate in a heterogeneous phase, comprising consecutively arranged apparatus for activating, acetylation and benzene washings, benzene stripping, partial saponification, water washings and final product drying. The apparatus for activating, the apparatus for acetylation and benzene washings, the apparatus for benzene stripping and the partial saponification apparatus are interconnected by connecting adaptors for conveying the fibrous reaction mass from one apparatus to another and provided with means for creating therein a sealing plug from the conveyed reaction mass. Said means for the creation of the sealing plug is in the form of a screw conveyer with a valve arranged atits discharge orifice and spring-loaded in the direction opposite to the direction of the fibrous reaction mass conveying 1 Claim, 3 Drawing Figures sis PATENTEU JAN 15 I974 saw 1 m 2 PLANT FOR CONTINUOUS PRODUCTION F CELLULOSE TRIACETATE IN A HETEROGENEOUS PHASE The present invention relates to plants for continuous 5 ping, partial saponification, water washings, and final I product drying. Between the apparatus for activating, acetylation and benzene washings, benzene stripping and partial saponification there are arranged connecting adaptors for conveying the reaction mixture from one apparatus to another, as well as for sealing separate apparatus containing explosion-hazardous substances: vapours of the acetylation mixture and benzene vapours.

Such apparatus are sealed by means which create a lock or seal from the conveyed fibrous reaction mixture, such means being arranged inside a connecting adaptor and consisting of a reciprocating piston. The walls of the connecting adaptor are perforated for removing the liquid component and are enclosed in a jacket. At the connecting adaptor outlet there is arranged a means for loosening the compacted heterogeneous phase of the reaction mass. 1

During the operation of the known plant, a fibrous reaction mass entering the connecting adaptor, due to the repeated reciprocations of the piston, is compacted and simultaneously freed from the liquid component which is drained through the perforated walls of the connecting adaptor. Y

I The thus squeezed heterogeneous phase of the reaction mass is pressed through the connecting adaptor to the loosening means and further to the subsequent apparatus.

However, in the known plant the means for creating a sealing plug fails to provide a possibility for regulating the compactness of the resultant plug and degree of squeezing out the heterogeneous phase of reaction mass depending on the intitial moisture content of the reaction mass and uniformity of its feeding.

Therefore any insignificant changes in the quantity of the reaction mixture entering the connecting adaptor and in its moisture content adversely affect the operation of the means creating the sealing plug. When the reaction mixture is fed in excess, a too compact plug is created, so that the piston is jammed in the cylinder. lnsufficient quantity of the reaction mass results in that the degree of its squeezing out is not sufficient.

Unreliable work of the means which creates the sealing plug leads to unstable operation of the entire plant. The use of this means for the creation of a sealing plug entails the necessity of providing an additional means for loosening the compacted heterogeneous phase which creates a large diameter plug at the connecting adaptor outlet.

As a result of the piston impact work, a considerable amount of the reaction mass fibres is carried away through the perforated walls of the connecting adaptors together with the squeezed out liquid component, which leads to losses of the reaction mass and complicates the liquid component conveyance and reuse.

In addition, continuous operation of all the apparatus in the known plant requires a coordination with the intermittent operation of the means which creates the sealing plug, this intermittent operation being due to the reciprocation of the piston. For this, it is necessary either to impart intermittent motion to the conveyer belt of the apparatus, or to use additional accumulating means with appliances for periodic feeding of the reaction mass portions to the connecting adaptor.

The compacted fibrous reaction mass leaves the connecting adaptor non-uniformly, pulse-wise, which creates difficult working conditions for the loosening means which either idles or works under excess load.

Sealing of the apparatus in the known plant can be provided only after a fibrous reaction mass plug has been created in the connecting adaptor. At the beginning of the plant operation as well as in case of its repair or stoppage for some other reasons, the apparatus creating explosion-hazardous conditions, need addiliese gxreassnsss f eati The object of the present invention is to provide a plant for the continuous production of cellulose triacetate in a heterogeneous phase in which the design of the means for the creation of a sealing plug ensures stable continuous operation of the plant, a reduction in the losses of the reaction mass fibres when creating a sealing plug and squeezing outthe liquid component as 129 1 assetsa tkina gudsi ns Said object is achieved in that in the plant for a continuous production of cellulose triacetate in a heterogeneous phase, comprising consecutively arranged apparatus for activating, acetylation and benzene washings, benzene stripping partial saponification, water washings and drying of the final product, the apparatus for activating, the apparatus for acetylation and benzene washings, the apparatus for benzene stripping and the apparatus for partial saponification are interconnected with the help of connecting adaptors for conveying the fibrous reaction mass from one apparatus to another and provided with a means for creating a sealing plug from the conveyed reaction mass; in accordance with the invention, the means for the creation of a sealing plug is in the form of a screw conveyer provided with a valve arranged near its discharge orifice, springloaded in the direction opposite to the direction of I travel of the conveyed fibrous reaction mass.

It is advisable that the connecting adaptor in which the screw conveyer is arranged should be mounted in an approximately horizontal position and provided with a longitudinal groove in its lower part, the groove being closed from the inside by a perforated plate protruding over the adaptor wall. 7

The proposed plant for a continuous production of cellulose triacetate in a heterogeneous phase features stable operation, produces a product of a stable quality, provides safeworking conditions, high efficiency and may be used for producing cellulose triacetate for making movie and still camera films and fibres.

The invention hereinafter is explained by an example of its possible realization with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic view of the plant for continuous production of cellulose triacetate in a heterogeneous phase, in accordance with the invention",

FIG. 2 shows a longitudinal section of the connecting adaptor together with the means for creating a sealing plug, in accordance with the invention and;

FIG. 3 is a section taken along the line III-III of FIG. 2.

The plant for continuous production of cellulose triacetate in a heterogeneous phase comprises the following main apparatus arranged in succession: an apparatus 1 (FIG. 1) for activating, an apparatus 2 for acetylation and benzene washings, an apparatus 3' for benzene stripping, a partial saponification apparatus 4 and a water washing apparatus 5.

The apparatus 1 for activating serves for preliminary treatment of cellulose with acetic acid and is made as an airtight chamber 6 in which a conveyer 7 with a perforated belt is located.

The apparatus 1 is provided with sprayers 8, a screw 9 distributing the cellulose over the width of the conveyer 7 a loosening means 10 in the form of a drum with sticks, and a screw collector 11.

The same design have the apparatus 2 for acetylation and benzene washings, the partial saponification apparatus 4, and the water washing apparatus 5.

Besides the sprayers 8, a plurality of self-priming pumps 12 for multiple circulation of benzene in the benzene washing zone is arranged in the apparatus 2 for acetylation and benzene washings.

The apparatus 2 for acetylation and benzene washings, the partial saponification .apparatus 4 and the water washings apparatus 5 are provided with an articulated placing conveyer 13 designed for levelling the cellulose layer from above and controlling its thickness. In each of the above-described apparatus under the conveyer 7 there are arranged baths 14 for removing the liquid component drain for the purpose of either its reuse or discharge to the sewerage.

The benzene stripping apparatus 3 is made as a screw arranged in an elliptical chamber.

The apparatus 1 for activating, the apparatus 2 for acetylation and benzene washings, the benzene stripping apparatus 3 and the partial saponification apparatus 4 are interconnected by connecting adaptors 15 for conveying the fibrous reaction mass from one apparatus to another and provided with a means for creating a sealing plug from the conveyed reaction mass.

The said means is made as a screw conveyer 16 (FIG. 2) on a shaft 17 of which'near its discharge orifice 18 a valve 19 is movably arranged, pressed by a spring 20 to the discharge orifice 18. The conical shape of the valve 19 allows the width of a circular clearance resulting as it is pressed away from the discharge orifice I8 to be essentially small. Therefore the compacted fibrous reaction mass emerges from this clearance in a thin layer according to the clearance width and does not need loosening by means of special equipment (the direction of travel of the reaction mass is shown in FIG. 2 by arrows).

The screw conveyer I6 helix does not reach the discharge orifice 18 for a distance equal to 0.1-1 body diameter, resulting in that at the discharge orifice 18 a compacting chamber for the conveyed fibrous reaction mass is created.

A spring 20 with its one end rests against a coupling 21 arranged on the shaft 17 with a possibility of axial movement and is protected from the effect of the aggressive medium by a jacket 22. The degree of squeezing the fibrous reaction mass or the size of the circular clearance between the valve 19 and the discharge orifice I8 is adjusted with the help of a nut 23, rigidly connected with the coupling 21, and a screw 24.

A trident 25 rigidly mounted on the shaft 17 is provided to prevent the heterogeneous phase from hanging over in a chamber 26 of the adaptor 15.

The means for the creation of a sealing plug also serves for squeezing out excess liquid component when the reaction mass is transferred from one apparatus to another. For this purpose the connecting adaptor I5 arranged in an approximately horizontal position is provided in its lower part with a longitudinal groove 27 closed from the inside by a perforated plate 28 extending over the wall of the adaptor I5. In addition, rapid and maximum draining of the liquid component is promoted in that the threads of the screw conveyer 16 are perforated and a perforated disc 29 and a nozzle 30 are arranged at the loading end of the adaptor 15. The plate 28 in its lower part is provided with transversal grooves 31 which form perforation slots after fixing the plate 28 over the longitudinal groove 27 by means of blocks 32 (FIGS. 2, 3). A collector 33 fixed from the outside to the adaptor 15 (FIG. 2) is designed for collecting the squeezed out liquid component drained through the nozzle 34.

The plate 28 in its upper part is provided with ports whose number corresponds to that of the transversal perforation slots. The diameter of these ports from the side of the plate 28 facing the screw conveyer I6 is sufficiently small to prevent heterogeneous phase particles from being entrained together with the liquid component. Nevertherless, said ports in their lower part are slightly widened and are equal to the width of the perforation slots.

Such an embodiment of the perforated plate 28 together with rapid draining of the liquid component prevents clogging of the perforations and entrainment of the fibrous heterogeneous phase since no mechanical action of the screw conveyer 16 takes place in the zone where the liquid component zone is drained off. In addition to the plate 28, inside the connecting adaptor 15 there are provided several other longitudinal plates 35 which present the reaction mixture fibres from being twisted by the screw conveyer l6 and which create conditions for the reaction mass translation movement to the discharge orifice 18 with the valve 19.

In the connecting adaptors 15 arranged after the apparatus 4 (FIG. I) for partial saponification and after the apparatus 5 for water washings there is also arranged a means for creating plugs from the reaction mass for the purpose of squeezing out the liquid component and further transfer of the squeezed out reaction mass by a pneumatic conveyer. However, for squeezing out the reaction mass after the partial saponification apparatus 4 and the water washings apparatus 5, another conventional means, such as a roll press, may also be used. For cellulose feeding into the apparatus l for activation use is also made of the adaptor 15 with the means for creating a sealing plug therein so as to prevent leakage of acetic acid vapours from the apparatus I.

The operation of the plant for continuous production of cellulose triacetate is as follows:

Loosened cellulose is loaded into the activating apparatus I through the adaptor l5 and is distributed by the screw 9 over the width of the conveyer 7 with a perforated belt. The activation is provided by abundantly spraying through the sprayers 8 of the cellulose layer transferred by the screw conveyer 7. At the end of the (cellulose, wetted with acetic acid) into the compacting chamber near the discharge orifice 18. In this chamber the fibrous reaction mass is compacted creat-.

ing a plug which seals the apparatus I (FIG. l) for activating, separating it from the apparatus 2 for acetylation and benzene washings, associated therewith through the connecting adaptor 115.

The reaction mass continues to enter into the connecting adaptor and there comes a moment when the sealingplug, overcoming the effort of the spring (FIGS. 1, 2) urges the valve 19 and creates a clearance at the discharge orifice 118 for the continuous exit of the compacted reaction mass. The liquid component (acetic acid) is squeezed out and drained through the perforated plate 28, the collector 33 and the nozzle 34. The liquid component is also drained through the perforated disk 29 and the nozzle 30. The squeezed out cellulose gets into the apparatus 2 (FIG. ll) for acetylation and benzene washings where it is again distributed by the screw 9 provided in the apparatus 2 over the width of the screw conveyer 7 of the apparatus 2. The cellulose layer on the screw conveyer 7 is levelled by the placing conveyer l3 and conveyed through the entire apparatus 2, being subjected first to spraying with the acetylating mixture resulting from acetic anhydride, benzene and acetic acid together with chlorinated lime as a catalyst, and then to benzene washings. The composition of the acetylating mixture is maintained constant by continuously adding the components. V W V V As a result of cellulose treatment with the acetylating mixture, fibrous cellulose triacetate is produced. Benzene washings serve to neutralize the catalyst remaining on the cellulose triacetate, Benzene circulation in the washing zones is provided by a plurality of selfpriming pumps 12.

At the end of the conveyer 7 of the apparatus 2 the resulting cellulose triacetate which contains liquid benzene is loosened by the loosener l0 and gets onto the screw collector Ill and further to the connecting adaptor l5, which connects the apparatus 2 with the apparatus 3 for benzene stripping. In this adaptor a sealing plug is created and benzene is partially squeezed out. I

The cellulose triacetate freed from benzene gets to the apparatus 3 for benzene stripping through the clearance at the discharge orifice of the connecting adaptor 15. In this apparatus the cellulose triacetate is sprayed with hot water and is subjected to treatment with live steam and then squeezed out with the formation of a sealing plug in the connecting adaptor 15 which connects the apparatus 3 for benzene stripping with the apparatus 4 for partial saponification.

In the apparatus 4 the cellulose triacetate layer, moving on the conveyer 7 with the perforated belt, is subjected to treatment with 10-12 percent nitric acid aqueous solution.

Partially saponificated cellulose triacetate, removed by the loosener II) from the belt of the conveyer 7 of the apparatus 4 by means of the screw collector ll gets into the connecting adaptor 15 arranged after the apparatus 4, is squeezed out and by the pneumatic conveyer through the conduit 36 is fed to the apparatus 5 for water washings. In this apparatus from five to six water washings of the cellulose triacetate are effected. The cellulose triacetate, washed and squeezed out in the adaptor 15, arranged after the apparatus 5, is delivered by the pneumatic conveyer through the conduit 37 to the apparatus for drying the final product (not shown).

The present invention permits continuous production of cellulose triacetate in a heterogeneous phase under stable and safe working conditions.

What we claim is:

1. A plant for continuous production of cellulose triacetate in a heterogeneous phase, comprising:

an apparatus for activating cellulose; an apparatus for acetylation and benzene washings, whose inlet is connected with the outlet of the said activating apparatus; an apparatus for benzene stripping, whose inlet is connected with the outlet of the said apparatus for acetylation and benzene washings; a partial saponification apparatus, whose inlet is connected with the outlet of the apparatus for benzene stripping; an apparatus for water washings, whose inlet is connected with the outlet of the said partial saponification apparatus; an apparatus for drying the final product, whose inlet is connected with the outlet of the said apparatus for water washings; connecting adaptors, which interconnect said apparatus for activating, apparatus for acetylation and benzene washings, apparatus for benzene stripping and partial saponification apparatus, and serving for conveying the fibrous reaction mass from one said apparatus to another; and apparatus for creating a sealing plug from the conveyed fibrous reaction mass in each of said adaptors which comprises a screw conveyer, a discharge orifice adjacent the discharge end of said screw conveyer, a valve arranged at said discharge orifice the valve being spring-loaded in the direction opposite to that in which the fibrous reaction mass is conveyed, the portion of said connecting adaptor in which said screw conveyeris arranged being located in an approximately horizontal position and being provided with a longitudinal groove in its lower part, and a perforated plate which closes said longitudinal groove and extends from the inside over the wall of said connecting adaptor, the groove and plate being provided for draining liquid components of the fibrous reaction mass, and a trident mounted behind said valve on a shaft and rotating therewith, said trident serving to prevent the accumulation of the reaction mass behind said valve. 

